Hiking - This is me getting a drink on a hike in Australia.

    

Gaming - Currently I am playing an old skool RPG.

 

I was born in 1973 in The Hague, The Netherlands, and grew up in Wassenaar, a small town that borders on the dunes. In 1992, I went to study Psychology at the University of Amsterdam, where I specialized in Psychological Methods. 

In these years I was mainly busy playing guitar and exploring Amsterdam. Like many others, I became a serious student only during the final years of my studies. In that period, with two fellow students I set up the Methodologiewinkel, where researchers can get advice on methodology, test theory, and statistics. I graduated in 1998, on an analysis of how methodological rules involving significance tests may influence scientific research practices.  

During my studies in methodology, I found philosophy of science to be an especially interesting field. Much to the amusement of my roommate, I had developed the habit of reading a book chapter or paper on that topic every day, during breakfast. I never thought I would really do anything with it career-wise, and diligently developed my skills in statistical modeling, expecting to find a job where I would do something useful, like data analysis. However, things worked out differently. More or less by accident (somebody else had quit the position) the opportunity arose in 1998 to do a Ph.D with Don Mellenbergh and Jaap van Heerden on the topic of test validity, in the research school IOPS. The project description sounded pretty vague, but I decided to take the opportunity anyway. That was one of the best choices I've made.

In the beginning of the project, I attempted to cook up additions and extensions to existing psychometric models; more or less the standard development for a psychometrician. However, when I proposed some of these to Don Mellenbergh and Jaap van Heerden, their reaction was lukewarm. 'Everybody does that,' said Don. 'Why don't you try to think about conceptual issues?'. So it turned out that my addiction to philosophy of science became very useful in analyzing the conceptual background of psychometric models, and I started to make attempts at writing theoretical articles. I soon found that this is an atypical activity for psychologists under sixty. In fact, various people told me that I better do something experimental or mathematical, or else I wouldn't last long - 'you cannot publish theoretical papers', is a warning I remember particularly well. I've learned from this that the best way to deal with advice is to listen carefully, nod politely, and then do your own thing anyway.

The project worked out better than anyone expected, I think (I later learned that some people had considered the entire Ph.D. project to be a recipe for disaster). The conceptual foundations of psychological measurement turned out to be relatively uncharted territory where reasonably straightforward investigations gave quite surprising results. In fact, thinking the usual psychometric practices through, one can stumble on immense problems in a few days, especially when Peter Molenaar is around to point them out to anyone who will listen (and to others as well). Some of the results are in this paper on latent variables, this paper on validity, and this one on measurement theory and psychometrics.

Anyway, I received my Ph.D. in 2003. After that, I went on to become Assistant Professor and then Associate Professor at the Psychological Methods Department of the University of Amsterdam. From 2004-2007 my research was sponsored by a Veni-grant from NWO. My dissertation was published by Cambridge University Press, and I received the Psychometric Society Dissertation Award for it. This led to a suggestion to submit something to the journal Psychometrika. I intended to write something on the philosophy of psychometrics, but instead I came up with a paper that laments some of the horrific psychometric practices we see in the social sciences, and urges psychometricians to get out of their hiding places and participate in empirical and theoretical discussions in psychology (which are dominated by people who are, let's say, stronger in the literary or practical aspects of scientific work). To my surprise they actually accepted the paper and I have since had many interesting discussions, with people from different fields, on the role of psychometrics in psychology.

I am currently working out alternative ways of thinking about the relation between theoretical concepts (like 'intelligence' or 'depression') and quasi-observables ('IQ-scores' or 'Insomnia') in terms of causal systems. This research is sponsored by a Vidi-grant from NWO; here is a paper outlining the major ideas, and here is a website dedicated to the project.

I also have life (see left).